In situations where the surfaces of metallic components engage and grind against one another, one or more of the contacting surfaces may be coated with an abrasive layer containing abrasive particles. The abrasive layer may act to protect the contacting surface of the component from wear, while enhancing the cutting/grinding strength of the component. For example, certain cutting instruments or grinding tools used in machining applications may have a cutting/grinding surface coated with such an abrasive layer. Similarly, the tips of rotating airfoils in gas turbine engines may be protected with an abrasive layer that wears away a surrounding abradable structure as the airfoil rotates. For instance, abrasive layers on the tips of turbine blades may wear away an abradable airseal lining a surrounding shroud as the turbine blade rotates to create a close-tolerance seal that prevents gas leakage, while also protecting the turbine blade tips from damage caused by the abrasion.
Current approaches to apply abrasive layers on gas turbine engine components, such as airfoils, frequently rely on electroplating methods to deposit the abrasive layers on desired part surfaces. The electroplating method may generally involve: 1) masking any surfaces of the part that are to remain uncoated, 2) placing the masked part in a plating bath containing dissolved metal ions, abrasive particles, and a metal anode, 3) applying a current to cause reduced metal(s) and abrasive particles to deposit on the unmasked surface of the part, and 4) unmasking the part. For example, U.S. Pat. No. 5,074,970 discloses the use of entrapment electroplating to co-deposit a nickel layer and abrasive particles on the tips of compressor airfoils. In this approach, the tip of the airfoil is submerged in a nickel plating solution containing a slurry of abrasive particles, and the deposition of a nickel layer on the airfoil tip causes the entrapment of any abrasive particles in contact with the tip in the nickel layer. As another example, U.S. Patent Application Publication Number 2010/0150730 describes the use of an electroplating method to apply an abrasive layer on the tips of turbine airfoils. While effective, the application of abrasive layers on component surfaces by electroplating may be limited by the size or structural features of the targeted surface due to line of site or current density issues. Moreover, electroplating may require relatively expensive equipment, particularly for plating applications on larger industrial parts, such as gas turbine engine parts. Even further, electroplating techniques may become complicated or cumbersome when dealing with larger parts and/or when complex masking/unmasking steps are required.
Clearly, there is a need for more efficient approaches for applying abrasive layers to component surfaces.